External pressure plate glazing element

ABSTRACT

This invention is an architectural glazing structure for exterior mounting that is a glass laminate having enhanced resistance to being pulled from a frame upon being subjected to severe positive and/or negative pressure loads. This invention is particularly suitable for architectural structures having windows that can be subjected to the extreme conditions prevalent in a hurricane, or window that can be placed under severe stress from repeated forceful blows to the laminate.

This application claims benefit of U.S. patent application Ser. No.10/817,628, filed Apr. 2, 2004, which matured into U.S. Pat. No.7,334,371, issued Feb. 26, 2008, which itself claimed benefit of U.S.Provisional Application No. 60/460,676, filed Apr. 4, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to laminated glass structures. This inventionparticularly relates to laminated glass structures that can withstandsevere impact and/or severe pressure loads.

2. Description of the Prior Art

Conventional glazing structures comprise a glazing element mounted in orto a support structure such as a frame. Such glazing elements cancomprise a laminate window, such as a glass/interlayer/glass laminatewindow. There are various glazing methods known and which areconventional for constructing windows, doors, or other glazing elementsfor commercial and/or residential buildings. Such glazing methods are,for example: exterior pressure plate glazing; flush glazing; marineglazing; removable stop glazing; and, silicone structural glazing (alsoknown as stopless glazing).

For example, U.S. Pat. No. 4,406,105 describes a structurally glazedsystem whereby holes are created through the glazing element and a platemember system with a connection being formed through the hole.

Threat-resistant windows and glass structures are known and can beconstructed utilizing conventional glazing methods. U.S. Pat. No.5,960,606 ('606) and U.S. Pat. No. 4,799,376 ('376) each describeslaminate windows that are made to withstand severe forces. InInternational Publication Number WO 98/28515 (IPN '515) a glass laminateis positioned in a rigid channel in which a resilient material adjacentto the glass permits flexing movement between the resilient material andthe rigid channel. Other means of holding glazing panels exist such asadhesive tapes, gaskets, putty, and the like and can be used to securepanels to a frame. For example, WO 93/002269 describes the use of astiffening member that is laminated to a polymeric interlayer around theperiphery of a glass laminate to stiffen the interlayer, which canextend beyond the edge of the glass/interlayer laminate. In anotherembodiment, '269 describes the use of a rigid member, which is insertedinto a channel below the surface of a monolithic transparency, andextending from the transparency.

Windows and glass structures capable of withstanding hurricane-forcewinds and high force impacts are not trouble-free, however. Conventionalglazing methods can require that the glazing element have some extraspace in the frame to facilitate insertion or removal of the glazingelement. While the additional space facilitates installation, it allowsthe glazing element to move in a swinging, rocking, or rotational motionwithin the frame. Further, it can move from side to side (that is, inthe transverse direction) in the frame depending upon the magnitude anddirection of the force applied against the glazing element. Underconditions of severe repetitive impact and/or either continuous ordiscontinuous pressure, a glass laminate can move within the frame orstructural support in such a way that there can be sufficient stressbuilt up to eventually fracture the window and allow the laminate to bepulled out of the frame. For example, when subjected to severe hurricaneforce winds the flexing movement in the windows of IPN '515, whereinglass flexes within a rigid channel, can gradually pull the laminate outof the channel resulting in loss of integrity of the structure. In '376,the glass held against the frame can be broken and crushed, causing aloss of structural integrity in the window/frame structure. In WO '269,inserting a stiff foreign body into the interlayer as described thereincan set up the structure for failure at the interface where the polymercontacts the foreign body when subjected to severe stresses.

WO 00/64670 describes glass laminates that utilize the interlayer as astructural element in glazing structures thereby providing greaterstructural integrity to the laminate during duress or after initialfracture of the glass.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a glazing element useful forexterior pressure plate glazing comprising a transparent laminate and anattachment means for attaching the laminate to a support structurewherein: (1) the laminate comprises at least one layer of glass bondeddirectly to a thermoplastic polymer interlayer on at least one surfaceof the glass; (2) the interlayer extends beyond at least one edge of thelaminate; (3) one surface of the extended portion of the interlayer isbonded to at least one surface of the attachment means; (4) anothersurface of the extended portion of the interlayer is bonded to theglass; (5) the attachment means is a clip useful for aligning andholding the laminate in a retaining channel of the support structure;(6) the clip further comprises at least one interlocking extensionuseful for restricting rotational and/or transverse movement of thelaminate within the channel and/or movement of the laminate out of thechannel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conventional glass laminate in a frame.

FIG. 2 is a glass/plastic/glass laminate of the present inventioncomprising a thermoplastic interlayer, wherein the laminate is held in achannel formed from a mullion and a pressure plate, the laminate beingheld in place with the assistance of an attachment means bonded to thethermoplastic interlayer.

FIG. 3 depicts a glazing element having a reduced moment arm comparedwith the glazing element of FIG. 2 due to a redesigned pressure plate.

FIG. 4 depicts a glazing element comprising an attachment means havingtwo symmetrical extensions and a redesigned mullion having recesses foraccepting and constraining one of the extensions.

FIG. 5 depicts an attachment clip having two symmetrical extensions anda flattened surface.

FIG. 6 depicts an attachment clip having two extensions that are notidentical.

FIG. 7 depicts an attachment clip having one extension and an adhesiveapplied inside the channel to restrict rocking of the glazing undernegative pressure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a conventional laminate comprising glass (1), athermoplastic interlayer (2) and glass (3), the glass being attached toa frame (4) through an intermediary adhesive layer (5) which istypically a gasket, putty, sealant tape, or silicone sealant.

The present invention is a glass laminate system that utilizes theinterlayer for the purpose of attaching the laminate to the supportstructure, as described in WO 00/64670, hereby incorporated byreference. In a process for producing glazing units for architecturalapplications that incorporate the interlayer as a structural element ofthe glazing, it has now been found that attaching the interlayer of aglass laminate to a support structure for the laminate can provideglazing units having improved strength and structural integrity againstsevere threats. The present invention relates to glazing elements thatare constructed for exterior pressure plate glazing applications andwhich utilize the interlayer to attach to the structural support.

In a conventional exterior pressure plate glazing application, theglazing element is typically inserted into a frame, which comprises amullion and a pressure plate. The mullion and pressure plate are usefulfor the purpose of providing an attachment for the glazing element tothe building or structure being fitted with the glazing element. Thepressure plate is used in concert with the mullion to hold the glazingelement securely in place in the frame. The pressure plate is attachedto the mullion using a fastener.

In one embodiment, the glazing element of this invention comprises asupport structure capable of supporting a glazing structure comprising alaminate having at least one layer of glass and at least onethermoplastic polymer interlayer that is self-adhered directly to atleast one surface of the glass. By self-adhered, it is meant that theinterlayer/glass interface does not require and therefore possibly maynot include any intervening layers of adhesives and/or glass surfacepre-treatment to obtain bonding suitable for use as a safety glass. Insome applications it is preferable that there is no intervening film oradhesive layer.

Thermoplastic polymers useful in the practice of the present inventionshould have properties that allow the interlayer to provide conventionaladvantages to the glazing, such as transparency to light, adhesion toglass, and other known and desirable properties of an interlayermaterial. In this regard, conventional interlayer materials can besuitable for use herein. Conventional interlayer materials includethermoplastic polymers. Suitable polymers include, for example;polyvinylbutyrals (PVB); polyvinyl chlorides (PVC); polyurethanes (PUR);polyvinyl acetate; ethylene acid copolymers and their ionomers;polyesters; copolyesters; polyacetals; and others known in the art ofmanufacturing glass laminates. Blended materials using any compatiblecombination of these materials can be suitable, as well. In addition, asuitable interlayer material for use in the practice of the presentinvention should be able to resist tearing away from a support structureunder extreme stress. A sheet of a suitable polymer for use in thepractice of the present invention has a high modulus, excellent tearstrength and excellent adhesion directly to glass. As such, a suitableinterlayer material or material blend should have a Storage Young'sModulus of at least 50 MPa at temperatures up to about 40° C. It can beuseful to vary the thickness of the interlayer in order to enhance thetear strength, for example.

While many conventional thermoplastic polymers can be suitable for usein the practice of the present invention, preferably the polymer is anethylene acid copolymer. More preferably the thermoplastic polymer is anethylene acid copolymer obtained by the copolymerization of ethylene anda α,β-unsaturated carboxylic acid, or derivatives thereof. Suitablederivatives of acids useful in the practice of the present invention areknown to those skilled in the art, and include esters, salts,anhydrides, amides, nitrites, and the like. Acid copolymers can be fullyor partially neutralized to the salt (or partial salt). Fully orpartially neutralized acid copolymers are known conventionally asionomers. Suitable copolymers can include an optional third monomericconstituent that can be an ester of an ethylenically unsaturatedcarboxylic acid. Suitable acid copolymers useful in the practice of thepresent invention can be purchased commercially from, for example, E.I.DuPont de Nemours & Company under the trade names of Surlyn® andNucrel®, for example.

In the practice of the present invention the edges of the interlayer canbe attached either directly to a support structure or indirectly to thesupport structure by way of an attachment means. As contemplated in thepractice of the present invention, a support structure can be anystructural element or any combination of structural elements that holdthe glazing element in place on the building or support the weight ofthe glazing element. The support structure can comprise a frame, bolt,screw, wire, cable, nail, staple, and/or any conventional means forholding or supporting a glazing element, or any combination thereof. Inthe present invention, “support structure” can mean the complete ortotal support structure, or it can refer to a particular structuralcomponent or element of the complete support structure. One skilled inthe art of glazing manufacture will know from the context which specificmeaning to apply. Direct attachment of the interlayer, as contemplatedherein, means a direct attachment of the laminate to the supportstructure or any element thereof wherein the interlayer is in direct andconsistent contact with the support structure. Direct attachment of theinterlayer to the support can be from the top, sides, bottom, or throughthe interlayer material. By indirect attachment it is meant any mode ofattachment wherein the interlayer does not have direct contact with thesupport structure, but does have contact with the support structurethrough at least one intervening structural component of the glazingelement. Indirect attachment of the interlayer to the support structureby way of an attachment means is most preferable in the practice of thepresent invention. The attachment means can be any means for holding orconstraining the glass laminate into a frame or other support structure.

In a preferred embodiment, the attachment means is an attachment clipthat can be bonded to an extended portion of the interlayer by a bondingprocess. In the practice of the present invention there is no directcontact intended between the clip and any portion of the glass layer(s)of the laminate, and any such contact is incidental. In any event, itcan be preferred to minimize contact between the clip and the glass inorder to reduce glass fracture under stress or during movement of thelaminate in the support structure. To that end, the portion of theinterlayer that extends from the edges of the laminate preferably formsan intervening layer between the clip and the glass layer such that theclip does not contact the glass. The surface of the clip that contactsthe interlayer can be smooth, but preferably the surface of the clip hasat least one projection and/or one recessed area, and more preferablyseveral projections and/or recessed areas, which can provide additionalsurface area for bonding as well as a mechanical interlocking mechanismwith the interlayer to enhance the effectiveness of the adhesive bondingbetween the dip and the interlayer, thereby providing a laminate/dipassembly with greater structural integrity.

In another embodiment, a conventional glass laminate unit can be used tocreate a laminate glazing unit of the present invention. To achieve thesame or similar effect as in other embodiments, the interlayer materialcan be bonded to the thermoplastic material without the necessity ofactually extending the interlayer beyond the edges of the laminate. Inthis embodiment, strips of thermoplastic polymer material suitable forbonding to the thermoplastic interlayer can be positioned on theperiphery of the laminate and heated to promote melting, or flow, of theinterlayer and the thermoplastic polymer on the periphery of thelaminate such that the two materials come into direct contact and becomeblended. Upon cooling below the melting point of the polymers, the twomaterials will be bonded to one another and thus be available to performthe bonding function between the glass and the attachment means. Otherprocesses for bonding the interlayer to the attachment means can becontemplated and within the scope of the present invention if theinterlayer is effectively extended outside the edges of the laminate bythat process. The thermoplastic polymer can be the same polymer as usedfor the interlayer, or it can be a different material that forms astrong enough bond with the interlayer material under the processconditions used. In a preferred embodiment bonding the thermoplasticstrips to the glass of the laminate and to the attachment means can beperformed simultaneously.

A bonding process suitable for use in the practice of the presentinvention is any wherein the interlayer can be bonded to the attachmentmeans. In the present invention, by “bonding” it is meant that theinterlayer and the attachment means form a bond that results in adhesionbetween the attachment means and the interlayer. Bonding can beaccomplished by physical means or by chemical means, or by a combinationof both. Physical bonding, for the purposes of the present invention, isadhesion that results from interaction of the interlayer with theattachment means wherein the chemical nature of the interlayer and/orthe attachment means is unchanged at the surfaces where the adhesionexists. For example, adhesion that results from intermolecular forces,wherein covalent chemical bonds are neither created nor destroyed, is anexample of physical bonding. Chemical bonding, according to the presentinvention, would require forming and/or breaking covalent chemical bondsat the interface between the interlayer and the attachment means inorder to produce adhesion.

The bonding process of the present invention preferably comprises thestep of applying heat to the dip while it is in direct contact with theinterlayer, that is, applying heat or energy to a clip/interlayerassembly such that the polymeric interlayer and the clip are bonded atthe interface where the clip and interlayer are in contact. Withoutbeing held to theory, it is believed that this results in a physicalbonding rather than a chemical bonding. Application of heat in thebonding process can be accomplished by various methods, including theuse of: a heated tool; microwave energy; or ultrasound to heat theinterlayer and/or the attachment clip and promote bonding. Preferablythe clip/interlayer assembly can be bonded at a temperature of less thanabout 175° C., more preferably at a temperature of less than about 165°C. Most preferably, the clip/interlayer assembly can be bonded at atemperature of from about 125° C. to about 150° C. Once bonded, theclip/interlayer/laminate form a laminate/clip assembly that can befitted or otherwise attached to a frame or other support structure.

A clip that is suitable for use in the practice of the present inventionhas a mechanical interlocking extension that can, by interlocking withthe support structure, reduce the motion available to the laminate inthe channel of a frame, or against any other rigid support structuremember. The extension member of the clip can thereby reduce the force ofthe rigid support structure against the laminate and also assist inholding the laminate in or to the support structure. The extensionmember can have various forms and/or shapes to accomplish its function.For example, the extension member can form part of a ball and socket; itcan form a “C”, an “L”, or a “T” shape to hold it into the supportstructure, or it can be any sort of extension arm such as a hook or aclamp, for example. Any design of the extension member, whichaccomplishes the function of facilitating the laminate being held intothe support structure, is contemplated as within the scope of thepresent invention.

For the purposes of this invention, a laminate/clip assembly of thepresent invention is said to be attached to a support structure if theassembly is nailed, screwed, bolted, glued, slotted, tied or otherwiseconstrained from becoming detached from the structure. Preferably, alaminate/clip assembly of the present invention is geometrically and/orphysically constrained within a channel formed by elements of aconventional framing structure. In the practice of the presentinvention, a conventional framing structure comprises a mullion whichfunctions to attach and hold a glazing element to a building, forexample. A framing structure useful in the practice of the presentinvention can comprise a pressure plate and a fastener which functionsto hold a glazing element in place against the mullion. Use of pressureplates and mullions in the glazing art for exterior glazing isconventional.

In one of the preferred embodiments of the present invention, depictedin FIG. 2, a glazing element (1) comprises: a glass (2)/interlayer(3)/glass (2) laminate; and an attachment clip (4). The glazing elementis contacted by gaskets (7), which assist in holding the glazing elementin a channel formed by a mullion (5) and a pressure plate (6). Theattachment clip comprises an interlocking extension (9), which projectsoutward and away from the outer edge of the laminate. The arm canfunction to restrict the movement of the glazing element within theframe channel (10) by cutting down on the rocking motion available tothe laminate upon being subjected to positive pressure at the surfacesof the laminate. In addition, the arm can assist in keeping the laminatefrom being pulled out by movement of the glazing element from side toside. The fastener (11) holds the pressure plate and mullion together,and can be tightened or loosened to apply more or less pressure to thegaskets holding the glazing element. A thermal separator (12) can beused for temperature insulation. The design depicted in FIG. 2 resultsin a laminate that can withstand either severe positive pressure ornegative pressure loads. The clip can optionally comprise an engagementhook at the end of the extension, to assist in retaining the laminate inthe frame channel.

In another embodiment depicted in FIG. 3, the glazing element showntherein is identical to the glazing element of FIG. 2. The mullion andpressure plate are identical to FIG. 2 except that the shape of thethermal separator (12) has been redesigned and inverted in order toreduce the moment arm of the glazing element. The reduced moment arm canfurther restrict the movement in the channel in a manner that canprevent sufficient force being generated to damage the laminate and/orallow the laminate to be pulled from the structure.

In another embodiment depicted in FIG. 4, the glazing element isidentical to the glazing element of FIG. 3, except that the attachmentclip (4 a) comprises a second extension arm (13), which functions tofurther promote retention of the glazing element in the channel (10)whether subject to either positive or negative pressure. The mullion ofFIG. 4 has a recess (14) to accept the additional extension arm.

In another preferred embodiment depicted in FIG. 5, the glazing elementis identical to the glazing element of FIG. 3, except that theattachment clip (4 b) has a flattened surface, which is more amenable tothe application of heat during the clip/interlayer bonding process. Themodified design of the clip in FIG. 5 can result in greater glasscapture or glass bite, of the laminate in the frame, which can result ingreater structural integrity for the glazing element. The mullion ofFIG. 5 is identical to the mullion of FIG. 4.

In still another preferred embodiment shown in FIG. 6, the glazingelement is identical to the glazing element of FIG. 3, except that theattachment clip (4 c) comprises a second extension arm (13 a) that isshorter than extension arm (9), and functions to promote retention ofthe glazing element in the channel (10) whether subject to eitherpositive or negative pressure. The mullion of FIG. 6 is identical to themullion of FIG. 3.

In still another preferred embodiment shown in FIG. 7, the glazingelement is identical to the glazing element of FIG. 3, except that theattachment clip (4) is bonded to the mullion by an adhesive (14). Whilean adhesive is optional in the practice of the present invention, use ofan adhesive in this manner does not require great skill and technicalprowess to apply the adhesive because the adhesive is not visibleoutside of the frame of the glazing element.

A laminate of the present invention has excellent durability, impactresistance, toughness, and resistance by the interlayer to cutsinflicted by glass once the glass is shattered. A laminate of thepresent invention is particularly useful in architectural applicationsin buildings subjected to hurricanes and windstorms. A laminate of thepresent invention that is attached or mounted in a frame by way of theinterlayer is not torn from the frame after such stress or attack. Alaminate of the present invention also has a low haze and excellenttransparency. These properties make glazing elements of the presentinvention useful as architectural glass, including use for reduction ofsolar rays, sound control, safety, and security, for example.

In a preferred embodiment, the interlayer is positioned between theglass plates such that the interlayer is exposed in such a manner thatit can be attached to the surrounding frame. The interlayer can beattached to the support structure in a continuous manner along theperimeter of the laminate. Alternatively, the interlayer can be attachedto the structural support in a discontinuous manner at various pointsaround the perimeter of the laminate. Any manner of attaching thelaminate to the frame by way of the interlayer is considered to bewithin the scope of the present invention. For example, the framesurrounding the laminate can contain interlayer material that can bondwith the laminate and also with the frame; the laminate can bemechanically anchored to the frame with a screw, hook, nail, or clamp,for example. Mechanical attachment includes any physical constraint ofthe laminate by slotting, fitting, or molding a support to hold theinterlayer in place within the structural support.

Air can be removed from between the layers of the laminate, and theinterlayer can be bonded, or adhered, to the glass plates byconventional means, including applying heat and pressure to thestructure. In a preferred embodiment, the interlayer can be bondedwithout applying increased pressure to the structure.

One preferred laminate of this invention is a transparent laminatecomprising two layers of glass and an intermediate thermoplastic polymerinterlayer self-adhered to at least one of the glass surfaces. Theinterlayer preferably has a Storage Young's Modulus of 50-1,000 MPa(mega Pascals) at 0.3 Hz and 25° C., and preferably from about 100 toabout 500 MPa, as determined according to ASTM D 5026-95a. Theinterlayer should remain in the 50-1,000 MPa range of its StorageYoung's Modulus at temperatures up to 40° C.

The laminate can be prepared according to conventional processes knownin the art. For example, in a typical process, the interlayer is placedbetween two pieces of annealed float glass of dimension 12″×12″ (305mm×305 mm) and 2.5 mm nominal thickness, which have been washed andrinsed in demineralized water. The glass/interlayer/glass assembly isthen heated in an oven set at 90-100° C. for 30 minutes. Thereafter, itis passed through a set of nip rolls (roll pressing) so that most of theair in the void spaces between the glass and the interlayer may besqueezed out, and the edge of the assembly sealed. The assembly at thisstage is called a pre-press. The pre-press is then placed in an airautoclave where the temperature is raised to 135° C. and the pressureraised to 200 psig (14.3 bar). These conditions are maintained for 20minutes, after which, the air is cooled while no more air is added tothe autoclave. After 20 minutes of cooling when the air temperature inthe autoclave is less than 50° C., the excess air pressure is vented.Obvious variants of this process will be known to those of ordinaryskill in the art of glass lamination, and these obvious variants arecontemplated as suitable for use in the practice of the presentinvention.

Preferably, the interlayer of the laminate is a sheet of an ionomerresin, wherein the ionomer resin is a water insoluble salt of a polymerof ethylene and methacrylic acid or acrylic acid, containing about14-24% by weight of the acid and about 76-86% by weight of ethylene. Theionomer further characterized by having about 10-80% of the acidneutralized with a metallic ion, preferably a sodium ion, and theionomer has a melt index of about 0.5-50. Melt index is determined at190° C. according to ASTM D1238. The preparation of ionomer resins isdisclosed in U.S. Pat. No. 3,404,134. Known methods can be used toobtain an ionomer resin with suitable optical properties. However,current commercially available acid copolymers do not have an acidcontent of greater than about 20%. If the behavior of currentlyavailable acid copolymer and ionomer resins can predict the behavior ofresins having higher acid content, then high acid resins should besuitable for use herein.

Haze and transparency of laminates of this invention are measuredaccording to ASTM D-1003-61 using a Hazeguard XL211 hazemeter orHazeguard Plus Hazemeter (BYK Gardner-USA). Percent haze is thediffusive light transmission as a percent of the total lighttransmission. To be considered suitable for architectural andtransportation uses. The interlayer of the laminates generally isrequired to have a transparency of at least 90% and a haze of less than5%.

In the practice of the present invention, use of a primer or adhesivelayer can be optional. Elimination of the use of a primer can remove aprocess step and reduce the cost of the process, which can be preferred.

Standard techniques can be used to form the resin interlayer sheet. Forexample, compression molding, injection molding, extrusion and/orcalendaring can be used. Preferably, conventional extrusion techniquesare used. In a typical process, an ionomer resin suitable for use in thepresent invention can include recycled ionomer resin as well as virginionomer resin. Additives such a colorants, antioxidants and UVstabilizers can be charged into a conventional extruder and melt blendedand passed through a cartridge type melt filter for contaminationremoval. The melt can be extruded through a die and pulled throughcalendar rolls to form sheet about 0.38-4.6 mm thick. Typical colorantsthat can be used in the ionomer resin sheet are, for example, a bluingagent to reduce yellowing or a whitening agent or a colorant can beadded to color the glass or to control solar light.

The polymer sheet after extrusion can have a smooth surface butpreferably has a roughened surface to effectively allow most of the airto be removed from between the surfaces in the laminate during thelamination process. This can be accomplished for example, bymechanically embossing the sheet after extrusion or by melt fractureduring extrusion of the sheet and the like. Air can be removed frombetween the layers of the laminate by any conventional method such asnip roll pressing, vacuum bagging, or autoclaving the pre-laminatestructure.

The Figures do not represent all variations thought to be within thescope of the present invention. One of ordinary skill in the art ofglazing manufacture would know how to incorporate the teachings of thepresent invention into the conventional art without departing from thescope of the inventions described herein. Any variation ofglass/interlayer/glass laminate assembly wherein a frame can be attachedto the interlayer—either directly or indirectly through an intermediarylayer, for example an adhesive layer, is believed to be within the scopeof the present invention.

For architectural uses a laminate can have two layers of glass and aninterlayer of a thermoplastic polymer. Multilayer interlayers areconventional and, can be suitable for use herein, provided that at leastone of the layers can be attached to the support structure as describedherein. A laminate of the present invention can have an overallthickness of about 3-30 mm. The interlayer can have a thickness of about0.38-4.6 mm and each glass layer can be at least 1 mm thick. In apreferred embodiment, the interlayer is self-adhered directly to theglass, that is, an intermediate adhesive layer or coating between theglass and the interlayer is not used. Other laminate constructions canbe used such as, for example, multiple layers of glass and thermoplasticinterlayers; or a single layer of glass with a thermoplastic polymerinterlayer, having adhered to the interlayer a layer of a durabletransparent plastic film. Any of the above laminates can be coated withconventional abrasion resistant coatings that are known in the art.

The frame and/or the attachment means can be fabricated from a varietyof materials such as, for example: wood; aluminum; steel; and variousstrong plastic materials including polyvinyl chloride and nylon.Depending on the material used and the type of installation, the framemay or may not be required to overlay the laminate in order to obtain afairly rigid adhesive bond between the frame and the laminateinterlayer.

The frame can be selected from the many available frame designs in theglazing art. The laminate can be attached, or secured, to the frame withor without use of an adhesive material. It has been found that aninterlayer made from ionomer resin self-adheres securely to most framematerials, such as wood, steel, aluminum and plastics. In someapplications it may be desirable to use additional fasteners such asscrews, bolts, and clamps along the edge of the frame. Any means ofanchoring the attachment means to the frame is suitable for use in thepresent invention.

In preparing the glazing elements of this invention, autoclaving can beoptional. Steps well known in the art such as: roll pressing; vacuumring or bag pre-pressing; or vacuum ring or bagging; can be used toprepare the laminates of the present invention. In any case, thecomponent layers are brought into intimate contact and processed into afinal laminate, which is free of bubbles and has good optics andadequate properties to insure laminate performance over the service lifeof the application. In these processes the objective is to squeeze outor force out a large portion of the air from between the glass andplastic layer(s). In one embodiment the frame can serve as a vacuumring. The application of external pressure, in addition to driving outair, brings the glass and plastic layers into direct contact andadhesion develops.

For architectural uses in coastal areas, the laminate ofglass/interlayer/glass must pass a simulated hurricane impact andcycling test which measures resistance of a laminate to debris impactand wind pressure cycling. A currently acceptable test is performed inaccordance to the South Florida Building Code Chapter 23, section 2315Impact tests for wind born debris. Fatigue load testing is determinedaccording to Table 23-F of section 2314.5, dated 1994. This testsimulates the forces of the wind plus air born debris impacts duringsevere weather, e.g., a hurricane. A sample 35 inches×50 inches(88.9×127 cm) of the laminate is tested. The test consists of twoimpacts on the laminate (one in the center of the laminate samplefollowed by a second impact in a corner of the laminate). The impactsare done by launching a 9-pound (4.1 kilograms) board nominally 2 inches(5 cm) by 4 inches (10 cm) and 8 feet (2.43 meters) long at 50feet/second (15.2 meters/second) from an air pressure cannon. If thelaminate survives the above impact sequence, it is subjected to an airpressure cycling test. In this test, the laminate is securely fastenedto a chamber. In the positive pressure test, the laminate with theimpact side outward is fastened to the chamber and a vacuum is appliedto the chamber and then varied to correspond with the cycling sequencesset forth in Table 1. The pressure cycling schedule, shown in Table 1,is specified as a fraction of the maximum pressure (P). In this test Pequals 70 PSF (pounds per square foot), or 3360 Pascals. Each cycle ofthe first 3500 cycles and subsequent cycles is completed in about 1-3seconds. On completion of the positive pressure test sequence, thelaminate is reversed with the impact side facing inward to the chamberfor the negative pressure portion of the test and a vacuum is appliedcorresponding to the following cycling sequence. The values areexpressed as negative values

TABLE 1 Pressure Range [pounds Number of Air Pressure per PressureCycles Schedule* square foot (Pascals)] Positive Pressure (inwardacting) 3,500 0.2 P to 0.5 P  14 to 35 (672-1680 Pascals) 300 0.0 P to0.6 P  0 to 42 (0-2016 Pascals) 600 0.5 P to 0.8 P  35 to 56 (1680-2688Pascals) 100 0.3 P to 1.0 P  21 to 70 (1008-3360 Pascals) NegativePressure (outward acting) 50 −0.3 P to −1.0 P −21 to −70 (−1008 to −3360Pascals) 1,060 −0.5 P to −0.8 P −35 to −56 (−1680 to −2688 Pascals) 50 0.0 P to −0.6 P  −0 to −42 (0 to −2016 Pascals) 3,350 −0.2 P to −0.5 P−14 to −35 (−672 to −1680 Pascals) *Absolute pressure level where P is70 pounds per square foot (3360 Pascals).

A laminate passes the impact and cycling test when there are no tears oropenings over 5 inches (12.7 cm) in length and not greater than 1/16inch (0.16 cm) in width.

Other applications may require additional testing to determine whetherthe glazing is suitable for that particular application. A glazingmembrane and corresponding support structure can fail by one of threefailure modes:

-   1. The glazing membrane breaches (a tear or hole develops) as a    result of a force being applied to the glazing or surrounding    structure.-   2. The glazing membrane pulls away or from the support structure    losing mechanical integrity such that the glazing membrane no longer    provides the intended function, generally a barrier.-   3. The support structure fails by loss of integrity within its    makeup or loss of integrity between the support structure and the    surrounding structure occurs.    Only failure modes 1 and/or 2 defined above are the subject of the    present invention.

The best-optimized system is defined herein as one where no failureoccurs in any component/subcomponent of the glazing system when themaximum expected ‘threat’ is applied to the glazing system. When somethreshold is exceeded, the ideal failure mode is one where a balance isachieved between failure modes 1 and 2 above. If the glazing membraneitself can withstand substantially more applied force or energy then thesupport structure has capability to retain the glazing, then the glazing‘infill’ is over-designed or the glazing support structure isunder-designed. The converse is also true.

EXAMPLES

The Examples are for illustrative purposes only, and are not intended tolimit the scope of the invention.

Examples 1 Through 3 and Comparative Examples C1 Through C3

Conventional glass laminates were prepared by the following method. Twosheets of annealed glass having the dimensions of 300 mm×300 mm (12inches square) were washed with de-ionized water and dried. A sheet (2.3mm thick) of ionomer resin composed of 81% ethylene, 19% methacrylicacid, with 37% of the acid neutralized and having sodium ion as thecounter-ion, and having a melt index of 2 was placed between two piecesof glass. A nylon vacuum bag was placed around the prelaminate assemblyto allow substantial removal of air from within (air pressure inside thebag was reduced to below 100 millibar absolute). The bagged prelaminatewas heated in a convection air oven to 120° C. and held for 30 minutes.A cooling fan was used to cool the laminate to ambient temperature andthe laminate was disconnected from the vacuum source and the bag removedyielding a fully bonded laminate of glass and interlayer.

Laminates of the present invention were prepared in the same manner asabove with the following exception. In some of the examples atriangular-shaped ‘corner-box’ retaining assembly as depicted in FIGS. 6and 9 of the present application, having a wall thickness of 0.2 mm anddimensions of 50 mm×50 mm×71 mm (inside opening of 10 mm) was placed oneach corner of the laminate after fitting pieces of ionomer sheet (2.3mm thickness) within the inside of the box thereby ‘lining’ the inside.The assembly was placed into the vacuum bag and the process above wascarried out to directly ‘bond’ the attachment to the interlayer. Tobetter insure that the laminates were free of void areas, that isentrained bubbles, areas of non-contact between the ionomer and glasssurface and that good flow and contact was made between the ionomer andthe inside of the ‘corner-box’ all laminates were then placed in an airautoclave for further processing. The pressure and temperature insidethe autoclave was increased from ambient to 135° C. and 200 psi in aperiod of 15 minutes. This temperature and pressure was held for 30minutes and then the temperature was decreased to 40° C. within a20-minute period whereby the pressure was lowered to ambient atmosphericpressure and the unit was removed.

A test apparatus similar to that described in SAE Recommended PracticeJ-2568 (attached as Appendix) was assembled to measure the degree ofmembrane integrity. The apparatus consisted of a hydraulic cylinder withintegral load cell driving a hemispherical metal ram (200 mm diameter)into the center of each glazing sample in a perpendicular manner,measuring the force/deflection characteristics. Deflection was measuredwith a string-potentiometer attached to the ram. The glazing sample wassupported either by a metal frame capturing the sample around theperiphery, only at the corners or any configuration where performanceinformation is desired. The data acquisition was done via an interfaceto a computer system with the appropriate calibration factors. Furthertreatment of the data was then possible to calculate the Maximum AppliedForce (F_(max)) in Newtons (N), and the deflection. Integration of thedata enabled the derivation the total energy expended in reaching afailure point of the glazing or supporting conditions. Testing of thelaminates was done after fracturing the laminate in order to moreaccurately measure the load-bearing capability of the interlayerattachment system.

Example C1 was an annealed glass plate (10 mm) that was stressed untilfracture. The test glazing had a standard installation with all foursides captured by the frame using a typical amount of edge capture (thatis, overlap of the frame and glass), and lined with an elastomericgasket.

Example C2 was a 90-mil polyvinylbutyral (PVB) laminate that wasprefractured. The laminate construction was a typical patch platedesign.

Example C3 was a 90-mil SentryGlas® Plus (SGP) laminate that wasprefractured and constructed with a typical patch plate design.

Example 1 was a laminate of the present invention, using a 90-milSentryGlas® Plus interlayer that was prefractured and constructed with afull perimeter attachment design (that is, the interlayer was attachedto the frame around the full perimeter of the laminate).

Example 2 was the same as Example 1, except that it was constructed witha corner attachment design.

Example 3 was the same as Example 2, except that a 180-mil SentryGlas®Plus laminate that was used.

To measure the relative performance of a glazing membrane capacityagainst an applied force/energy and the capability for the glazingsupport structure (or means) to retain the glazing the following testingwas performed. The displacement (D), which is defined as the distancetraveled by the ram from engaging the laminate to the point of laminatefailure, was measured. The membrane strength to integrity (S/R) ratiowas measured. The S/R ratio is defined as the ratio of the appliedenergy required to cause a failure in a given laminate over the appliedenergy required to break C1. The performance benefit (B) over thetraditional patch plate design was calculated by dividing the appliedenergy required for failure in the laminate by the applied energyrequired to for failure in C3. The resulting data is supplied in Table2.

TABLE 2 F_(max) Ex D (mm) (N) S/R B C1 9 5284 1 .02 C2 122 108 22 .5 C365 939 45 1 1 80 11595 408 9.1 2 80 7243 274 6.1 3 90 9003 452 10.0

Examples 4 through 10 and Comparative Example C4 Laminates were preparedusing 9/16″ thick laminated glass incorporating 0.090″ thick SentryGlas®Plus, available from E.I DuPont de Nemours and Company (DuPont) and ¼″heat strengthened glass. In all but one respect this is a common glazingalternative used in commercial glazing applications for large missileimpact resistance. The improvement over the existing industry standardsis the attachment means used, that is, bonding of aluminum profiles tothe laminated glass' interlayer edge with a contact-heating device. Thealuminum profile was a “u” channel shape with a leg extending from thebase of the “u” engaging an interlocking profile design in a customextruded pressure plate. The 12″ long aluminum profiles were positionedaround the glass edge in strategic locations to determine the mostoptimal location for load transfer within the glazed system. Theattachment means geometry used for design validation was purposelydesigned to minimally impact the framing system into which it wasinstalled. Because of this, the structural performance on inward actingair pressure cyclical loads behaved differently within the system thanoutward acting air pressure loads. This allowed for validation that thedesign of the attachment means of the present invention did indeedprovide a substantial improvement over conventionally dry glazedsystems.

Eight different individual test specimens were subjected to the testprocedures required for large missile impact resistance with thelocation of the attachment means of the present invention varying witheach test specimen. Example C4 was tested without any attachments of thepresent invention to define a baseline performance standard for adry-glazed application with ½″ glass bite. Each test specimen was 63″wide×120″ high and was mounted in a steel test frame to simulate apunched opening installation in a building.

All of the tested specimens passed the required impact resistance with a2″×4″ wooden missile weighing 9# and traveling at 50 feet/second. Theresults of the cycling test for the various test specimens are shown inTable 3. Pressure cycling was conducted according to the PressureSchedule shown in Table 1. A laminate of the present invention is givena passing mark for (+) load if the laminate holds in the supportstructure at 4500 cycles in the positive load direction and a passingmark in the (−) load direction at 4500 cycles in the negative loaddirection. The test laminates (with the exception of the comparativeexample) were designed so that the attachment means of the presentinvention was only engaged in the (+) load direction, and retentionunder negative load would be nearly identical to conventional laminates.

The units that failed in the negative load direction demonstratedprecisely how much of an improvement the attachment means provided theinstallation. Given that without the attachment means, the limitationfor a framing of this type, dry-glazed, with ½″ glass bite is about a 50PSF design pressure differential. Through testing at least a doubling ofthe effective design pressure differential to 100 PSF was demonstrated.It is contemplated that higher-pressure loads would have been obtainablehad the interior extruded aluminum profiles been designed to accept theattachment clips as well.

TABLE 3 Ex Pressure Results Cycles (no.) C4  +/−50 PSF Passed +/− loads9000 4 +/−100 PSF Failed + load 4424 5 +/−100 PSF Failed + load 3800 6+/−100 PSF Failed + load 4416 7 +/−100 PSF Passed + load 4509 8 +/−100PSF Passed + load 4502 9 +/−100 PSF Failed + load 4409 10  +/−100 PSFPassed + load 4500

Examples 11 Through 15, C5 and C6

Laminates of the present invention were constructed similarly to FIGS. 2and 3 (Examples 11-13) and FIGS. 4 and 5 (Examples 14 and 15). Thetensile force required to failure was measured on unbroken laminates andon intentionally broken laminates. Examples 13 and 14 utilized aluminum(Al) frames which were modified with grooves to allow the polymer toflow into channels in the surface of the frames, creating additionalmechanical interlocking of polymer to frame. The results are shown inTable 4.

TABLE 4 Pre-test Tensile Example Frame Style Damage Force (lbs) C5gasket unbroken 24.7 C6 silicone unbroken 40.7 11 Aluminum unbroken265.9 12 Aluminum broken 166.7 13 Al(grooved) broken 77.4 14 Al(grooved)unbroken 440.1 15 Aluminum broken 210.4

1. An exterior pressure plate glazing element comprising a transparentlaminate and an attachment means for holding the laminate in, orattaching the laminate to, a support structure, the support structurehaving a retaining channel formed therein, (a) a laminate having atleast one glass layer bonded to a thermoplastic polymer interlayer, theglass layer having first and second planar surfaces and an edge, thethermoplastic polymer interlayer being directly bonded to one of theplanar surfaces of the glass layer, a portion of the thermoplasticpolymer interlayer extending past and overlying the edge of the glasslayer, and (b) an attachment clip for holding the laminate in orattaching the laminate to the support structure, the attachment clipincluding a mounting portion and an arm, the mounting portion of theattachment clip being bonded directly to the extending portion of thethermoplastic polymer interlayer, the arm extending away from themounting portion in a direction that is generally perpendicular to theplanar surfaces of the glass layer, a portion of the arm projecting intothe retaining channel to align and hold the laminate therein, theprojecting portion of the arm interlocking the laminate to the supportstructure thereby to restrict rotational and/or transverse movement ofthe laminate within the channel or movement of the laminate out of thechannel.
 2. The glazing element of claim 1 wherein the thermoplasticinterlayer is an ethylene copolymer.
 3. The glazing element of claim 2wherein the interlayer is an ethylene copolymer comprising repeatingunits of an α,β-unsaturated carboxylic acid and/or a derivative thereof.4. The exterior pressure plate glazing element of claim 1 wherein theretaining channel is formed by a mullion and a pressure plate.
 5. Theexterior pressure plate glazing element of claim 4 wherein the glazingelement is contacted by gaskets which assist in holding the glazingelement in the channel.
 6. The exterior pressure plate glazing elementof claim 1 wherein the laminate further comprises: a second glass layerhaving first and second planar surfaces and an edge thereon, one of theplanar surfaces of the second glass layer being bonded to thethermoplastic polymer interlayer with a portion of the thermoplasticpolymer interlayer extending past and overlying the edge of the secondglass layer, thereby to form a glass/interlayer/glass laminate.
 7. Theexterior pressure plate glazing element of claim 1 further comprising afastener that holds the pressure plate and mullion together, and thatcan be tightened or loosened to apply more or less pressure to thegaskets holding the glazing element.